Just over an hour after partnering Kauto Star to victory in the JNwine.com Champion Chase, Walsh suffered the injury after coming to grief on Corrick Bridge in the Rainbow Telecom Handicap Chase.
The jockey reports his subsequent operation to have gone well and he is trying to remain upbeat.
“The operation all went well yesterday and I’ll be back home tomorrow,” said Walsh.
“I reckon I’m looking at 12 weeks out. I heard one newspaper said I could be out for six months – but I haven’t broken my neck!
“These things happen and you can’t all be doom and gloom about it, and at least I’ll get a chance to spend some time with my family.”
Meanwhile, Sam Thomas is set to be reunited with Denman when he bids to win the Hennessy Gold Cup for the third time on November 27.
Thomas was on board the 10-year-old when he took the Newbury highlight in 2007, while they also tasted Cheltenham Gold Cup glory together in 2008.
After winning the Hennessy under Ruby Walsh 12 months ago, champion jockey Tony McCoy took to the saddle for the remainder of the campaign.
But with Walsh sidelined with a broken leg and McCoy expected to be retained by his boss and leading owner JP McManus, connections have once again turned to Thomas.
Denman’s owner Paul Barber said: “I shall be very surprised if Sam doesn’t ride Denman in the Hennessy and I hope he wants to ride him.
“We haven’t actually offered Sam the ride, but he knows all about it. The horse is in very good form.”
McManus is far from certain to have a runner in the Newbury highlight, however, with his two entries Quiscover Fontaine and Arbor Supreme not guaranteed to line up.
“We’ll have to see a bit nearer the time. Willie (Mullins) says the pair of them are getting there but whether he can get a run into them beforehand, I don’t know,” said the owner’s racing manager Frank Berry.
“Willie’s horses are a bit behind at the moment and I would say they’ll be doing well to make the race, but we will know more nearer the time.”
Should McManus not be represented, this would leave McCoy free to take another ride in the race, with speculation bound to arise that he will get the leg-up on dual Cheltenham Gold Cup hero and Denman’s stable companion Kauto Star.